施加外源稀土元素对土壤中氮形态转化和有效性的影响

Influence of rare earth elements on chemical transformation of nitrogen in agricultural soil.

通过温室土培试验 ,测定了施加不同剂量农用稀土微肥 (常乐 )后不同采样时间的土壤有效N、NH+4 N、NO-3 N含量和土壤脲酶活性 .结果表明 ,当外源稀土施入量较大时 ,土壤有效N和NH+4 N含量明显降低 ,而土壤NO-3 N的变化不显著 .根据化学品安全性评价方法 ,实验确定外源稀土对土壤NH+4 N和有效N浓度影响的无观察效应浓度 (NOEC)应为 5mg·kg-1风干土 .实验观察到土壤NH+4 N含量的降低与土壤脲酶活性的抑制之间有较好的相关性 (R2 =0 .87) .外源稀土对土壤N形态转化和有效性产生影响的主要原因之一 ,是外源稀土施入量较高时抑制了土壤脲酶参与下的氨化作用 .土壤生态系统可以通过自适应过程进行自我调节 ,恢复N供给的能力 .

Soil available N,NH + 4-N and NO - 3-N contents and soil urease activity were measured after application of rave earth elements(REEs).The results showed that the contents of soil available N and NH + 4-N were affected by application of REEs,being significantly differed from those in the control when the dosage was higher than 5mg·kg -1 dry soil.However,soil NO - 3-N content in treated plots did not differed from that in the control.No observed effect concentration(NOEC) for the potential influnence of REEs on the chemical transformation and availability of soil available nitrogen was found to be 5mg·kg -1 dry soil.The decrease of soil available N concentration was found closely correlated to the inhibition of soil urease activity (R 2=0.87).It was suggested that the inhibition effect of REEs on the enzymatic nitrogen mineralization should be one of the major causes for the decline of soil available nitrogen concentration.The decrease of available nitrogen concentration occured shortly after REEs application,indicating that there should be a self-regulation process to maintain the available nitrogen concentration in soil.